To achieve comparability, standardized testing programs such as the ones offered by ARDMS report scaled scores. The reported scaled scores are obtained by statistically adjusting and converting raw scores onto a common scale to account for differences in difficulty across different test forms. For an easier test form, a test taker needs to answer slightly more questions correctly to get a particular scaled score. For a more difficult test form, a test taker can get the same scaled score answering slightly fewer questions correctly.
Using scaled scores enables test results to be reported consistently from one test form to another. Though test forms are designed to be as similar as possible, slight differences do occur. Scaled scores, however, maintain their meaning over time and test forms, so if two examinees achieve the same scaled score on two different test forms, they will have demonstrated the same attainment. In the scaled score for the ARDMS tests, 555 will always represent the ‘minimum standard’ but the ‘raw score’ (the total number of correct answers) that equates to it may be slightly different from one test form to another